best way to explain it the cars talk to the base on one freq and the base to cars on one freq.
its not a repeater system.i think its called a duplex system. there are a couple of old state dps dispatchers on here give them some time the will respond to you.
Duplex means two channels are used: one in each direction.
Duplex channel systems transmit and receive on different discrete channels. This defines systems where equipment cannot communicate without some infrastructure such as a repeater, base station or Talk-Through Base. Most common in the US is a repeater configuration where a base station is configured to simultaneously re-transmit the audio received from mobile units. This makes the mobiles, or hand-helds, able to communicate amongst one another anywhere within reception range of the base station or repeater. Typically the base or repeater station has a high antenna and high power, which allows much greater range, compared with a ground vehicle or hand-held transceiver.
Duplex systems can be divided into two types. The term half-duplex refers to systems where use of a push-to-talk switch is required to communicate. Full duplex refers to systems like mobile telephones with a capability to simultaneously receive and transmit. Repeaters are by nature full duplex, most mobiles and almost all handhelds are half duplex.
Advantage: duplex channels usually allow repeater operation which extends range (in most cases due to increased transmit power and improved aerial location / height) - especially where hand-held radios are in use.
Disadvantage: If a radio cannot reach the repeater, it cannot communicate.
To keep it real simple. You need to be real close to hear the car audio. With an outside antenna I can get about a 30 mile range. The car uses one frequency and the base uses another frequency. Don't use a delay on both frequencies. Also program the base first then the car frequency in that order.